The present invention relates to an internal antenna built in a portable terminal for a mobile communication; and, more particularly, to a small-sized built-in antenna formed into a zigzag-shaped radiation element of metal material and having high radiation efficiency and a wideband characteristic.
Recently, antennas used in the most of portable terminals are external antennas of monopole and helical types having a length of xcex/4 (xcex is a wavelength of a using frequency) or a retractable type combining the monopole and helical types. Since the above antennas are basically positioned at an outside of the portable terminal, it is difficult to reduce a size of the portable terminal. Accordingly, a research of a built-in antenna capable of being packaged within the portable terminal has been developed in order to reduce a size of the portable terminal.
A microstrip patch antenna technology using a printed circuit board (PCB), a ceramic chip antenna technology using a high dielectric material and an inverted F-type antenna technology have been recently developed. As the size of the antenna is reduced, these built-in antennas have a problem that a characteristic of an antenna is deteriorated due to an antenna design. Since the inverted F-type antenna uses a probe feeding way to feed signals to a radiation element, it has a very narrow bandwidth so that it is limited for a service requiring a wideband. When the ceramic antenna is used as a built-in antenna, a high dielectric material should be used to reduce a size of the antenna, however a gain loss of the antenna is caused. The microstrip patch antenna technology using the printed circuit board has advantages in that frequency tuning and bandwidth extension are possible by using various slot technologies and stacking technologies. However, it has a disadvantage that a volume of the antenna is highly increased.
FIG. 1 is a schematic view showing portable terminals having external antennas. A helical antenna 11 and a retractable antenna 12, which are generally used in the portable terminal, are shown. Since these antennas have a narrow bandwidth and a single band, it is limited for a system requiring a wide bandwidth. Also, since the antennas are positioned at an outside of the terminal, a specific absorption rate, which is affected on the human body, is high and undesired radiation waves are generated around the terminal.
It is, therefore, an object of the present invention to provide a wideband built-in antenna in a portable terminal for a mobile communication, which is capable of reducing a size of the antenna and obtaining a wideband effect by an electromagnetic coupling effect.
In accordance with an aspect of the present invention, there is provided a wideband built-in antenna in a portable terminal, comprising a radiation means for radiating radio waves, wherein the radiation means is formed into a zigzag-shaped conductive line having predetermined thickness and width.
In accordance with another aspect of the preset invention, there is provided a wideband built-in antenna in a portable terminal for mobile communication, comprising: a ground plate electrically connected to a ground of the portable terminal; a radiation means formed with a zigzag shaped conductive line having predetermined thickness and width in parallel with the ground plate at a predetermined distance; a feeding point for feeding signals to the radiation element; a feeding probe for connecting the radiation element to the feeding point; and a fixing means for fixing the antenna to the portable terminal.